Collapsible automobile body structure and method of making same



United States Patent 1111 3, 47,

[72] Inventor Walter S. Eggert,.lr. [56] References Cited "WingdonValley, UNITED STATES PATENTS 1 Ql A r fi 3,171,669 3/1965 Barenyi280/106 d 1970 2,870,871 1/1959 Stevinson.. 293/52F 3,437,367 4/1969Blank 293/52F [73] Asslgnee The Budd Company Philadelphia, Pa. PrimaryExaminer-Philip Goodman Attorneys-Thomas l. Davenport, Edward M.Farrell, Alford a corporation of Pennsylvania COLLAPSIBLE AUTOMOBILEBODY STRUCTURE AND METHOD OF MAKING SAME 3 Claims, 4 Drawing Figs.

U.S. Cl. 280/106, 293/52 Int. Cl. 862d 21/00 Field of Search 280/ l 06;

L. Trueax, Jr. and William R. Nolte ABSTRACT: A vehicle frame structurefor providing progressive collapse of a vehicles body during collisionwithout the high stress of the initial contact. The structure for sticha reaction being provided by prestressed frame components.

PATENTED new 519m 3547;463

SHEET 1 [IF 2 INVENTOR.

WALTER S. EGGERT,JR.

ATTORNEY PATENTEI] mini 5 I976 sum 2 0F 2 STRESS (UNSTRESSED COMPONENT)STRAIN PRESTRESSED COMPONENT STRESS A STRAIN Fig.4

INVENTOR.

WALTER S. EGGER'LJR.

ATTORNEY COLLAPSIBLE AUTOMOBILE BODY STRUCTURE AND METHOD OF MAKING SAMEWith the increased emphasis on safe motor vehicles, the presentinvention has been developed to protect vehicle passengers from theinitial shock of impact. I-Ieretofore it has been the general practiceto design special structure, such as V" notches, holes and flutes instructural member, to provide progressive collapse of vehicle during acollision,

It is an object of this invention to show a method and means ofconstructing automobile structures as either components or assembliesthat have and maintain predetermined collapse characteristics. I

This invention is concerned primarily with the separate underframe of aconventional vehicle body or the stub front side rails of a monocock orunitized vehicle body. The previous art attempted to provide aprogressivelycollapsible vehicle front end by specially designedstructures forcollapse in a preferred direction. iAnother object of thisinvention is to convert'a typical frame structure to one having aprogressive collapse characteristic.

Referring now to the drawing, there is shown:

FIG. I is a plan view, with portions broken away, of a front end of atypical separate underframe for a vehicle body having one bumper supportextension in the unstressed condition and the other bumper supportextension in the prestressed or finished condition. v

FIG. 2 is a plan view, with sections broken away, of the front end of anunitized body showing the one, stub rail in the unstressed condition andthe other stub 'rail in the prestressed condition.

FIG. 3 shows a typical stress-strain curve for a front-end collision ofan automobile.

FIG. 4 shows a stress-strain curve for a front-end collision of anautomobile having prestressed components of this inven tion.

Referring now to the drawings, as best seen in FIG. 1, a vehicle fromfor supporting an automobile body of a separate underframe type vehicleis shown 'with one front bumper side member extension 12 shown in theunstressed condition and the other front bumper side member extension 14shown in the prestressed condition, In'FlG. 2, the front-end structure16 of a unitized or monocock-vehicle is shown with one stub rail 18 inthe unstressed condition and the other stub rail in the prestressedcondition.

It was found that in a typical automobile front-end collision, astress-strain curve such as that shown in FIG. 3 was formed. Referringto FIG. 3, as the stress or force per unit area increases the strain orchange per unit length remains small until the metal of the automobilereaches the upper yield point at 22. From point 22 the metal starts toyield until the lower yield point 24 is reached and the continuedapplication of a constant stress force is absorbed by the yielding ofthe metal along a substantially constant stress level as the front ofthe vehicle crumples. The intent of this invention is to eliminate theinitial high stress required to begin the controlled collapse of thefront body structure of an automobile so that the stress-strain curvewill begin at point A. j

It was found that automobile components and assemblies could beprestressed under controlled conditions until reapplication of stress tothe automobile will provide a curve as shown in FIG. 4, where thestress-strain curve begins at point To accomplish the desiredcharacteristics of FIG. 4, the underframe of FIG. 1 or the front stubrails of a unitized body, FIG. 2, are initially fabricated longer thanrequired for final assembly. Then the frame is held in jigs'and fixtureswhich prestresses the components in a preferred direction, thuseliminating the high-strr sS portion 22-of the curve shown in FIG. 3 andproducing a component of the proper length. By initially upsetting orstraining the component or assembly in the direction in which theexpected collision force will be applied, the prestressed component orassembly may be used in an automobile body without harmful effects tothe automobile body structure. However, once the prestressed componentsor assembly ll'lCLllS forces due to collision, the structure collapsesunder a constant stress force so as to provide the preferred shockcollision characteristics of the stress-strain curve in FIG. 4.

Thus, it can be seen by reference to FIG. 3, and FIG. 4, the prestressedstructure has eliminated the high stress required in the unstressedcomponents to provide collapse of the body structure without the initialhigh stress or s'hock.

This method may be applied to individual components as well as theassembled underframe.

l. A frame in a vehicle body structure for absorbing impact forces andhaving preferred directional collapse character'istics, said framehaving a pair of longitudinally extending substantially parallel sideframe members, a-plurality of cross members extending between said sideframe members and having each end of each crossmember secured to theadjacent side frame member, each of said side frame members having anend section extending beyond the last crossmember, said end sectionshaving end portions for supporting a bumper and intermediate portionsextending betweensaid end portions and the last crossmember attachingpoint, said intermediate portions having buckled areas stressed byapplication of a longitudinal compressive force to plastically deformsaid intermediate portion beyond the elastic limit of the material andform said end frame sections to the proper length, and said buckledintermediate portions having longitudinal collapse characteristics whenexposed to forces above the yield point of the material.

2. The frame as claimed in claim l'wherein said side frame members havea substantially U-shaped cross section.

3. The frame as claimed in claim 1 wherein said side frame members havesubstantially rectangular cross sections and said buckled intermediateportions extend inwardly and outwardly of the planes of the rectangularsides of the frame members.

